An electrochemical device comprising a nonaqueous electrolyte composition between opposed electrodes is used as a display device or a secondary battery. Such an electrochemical device has problem in the electrolyte composition used. A liquid electrolyte composition employing a nonaqueous solvent or an ionic liquid, although it is excellent in ion conductivity, has problem in that mechanical strength is poor and leaking of the liquid is likely to occur, resulting in poor handling property. Therefore, in order to overcome the problem, various attempts have been made in which the liquid electrolyte composition is added with materials such as a viscosity increasing agent or a gelling agent to be gelled or solidified. Particularly in a thin electrochemical device proposed in recent years, an electrolyte composition is required to be formed into a uniform film with high strength. However, when the strength of the film increases, migration of ions in the electrolyte composition tends to be inhibited, which results in lowering of the electrochemical reaction speed.
In order to solve the problem above, a gel electrolyte composition containing a gelling agent having a molecular weight of not more than 1000 has been proposed (disclosed, for example, in Japanese Patent O.P.I. Publication No. 11-185836). There is description therein that such a gel electrolyte composition provides a dye sensitization photoelectric conversion device or a photo-reproduction photo-electrochemical battery which excels in photoelectric conversion efficiency and in durability. However, it has proved that even the gel electrolyte composition has still problem in attaining both high electrochemical reaction efficiency and high film strength.
There is a general disclosure of solidification or gelation of an electrolyte composition of an electrochromic device in Japanese Patent O.P.I. Publication No. 2004-151265, however, there is no disclosure therein of effects other than the above effects of the solidification or gelation nor concrete embodiments.
In view of the above, a means has not been found hitherto to solve a problem in which performances vary due to variation of moisture content of an electrolyte composition particularly in an electrochemical device comprising the electrolyte composition.